1. Field Of the Invention
The invention relates to a method of producing a (meth)acryloylthio compound, starting from (meth)acrylic acid anhydride.
2. Discussion of the Background
The preparation of esters of thiocarboxylic acids, which esters are categorized as "active esters", may be regarded. as a process starting with reactive carboxylic acid derivatives. Thus, e.g., hitherto (meth)acryloylthio esters have been produced preferably from the corresponding carboxylic acid. halides (see Koton, M. M., et al., 1956 Zh. ObShch. Khim. 26, 475-6; CA 50:13815; JP 2-229,808 and JP 3-011,054). The synthesis of bis(meth)acryloylthio) compounds from 3-chloro-(2-methyl)propanoic acid chloride and dithiols is the subject of JP 02-172,969. In JP 02-003,675, the preparation of (meth)acryloylthio esters from (meth)acryloyl chloride with phase transfer catalyst is described. Bis{(meth)acryloylthio}compounds may also be produced by this general method, as described in EP-A 273,661.
Reaction of (meth)acrylic acid halides gives rise to a number of problems. Thus, e.g., (meth)acrylic acid chloride has a pungent odor, fumes when exposed to air, and is a potent eye irritant; further, it has a tendency to homopolymerize. Acryloyl chloride is readily volatilized, is a strong irritant to mucous membranes, and readily homopolymerizes in light. (See Rauch-Puntigam, H., and Voelker, Th., 1967, "Acryl- und Methacrylverbindungen", pub. Springer-Verlag, of Berlin, Heidelberg, and New York, pp. 19 and 43.) Accordingly the problem is presented of devising a method of producing esters of (meth)acrylic acid and aromatic or aliphatic thiols which method does not employ acid halides. A consideration is that as the activation of the carbonyl function is decreased the probability of reaction at the double bond is increased, e.g., by addition of nucleophiles, or addition polymerization.
When thiols are reacted with (meth)acrylic acid derivatives having a decreased carbonyl reactivity than that of an acid halides, one must take into account 1,4-addition of the thiol to the activated double bond. (See Houben-Weyl, 1955, "Methoden der organischen Chemie" 4th Ed Vol IX, pub. Georg Thieme-Verlag, pp. 124-125.) Molecules with two (activated) double bonds in the molecule, such as, e.g., (meth)acrylic acid anhydride, have enhanced addition capability, so that reaction to form the thiolic ester would not be expected. Counter to expectation, however, it has been discovered, in connection with the present invention, that (meth)acryloylthio compounds can be produced by reacting a thiol with (meth)acrylic acid anhydride.